SQLAlchemy - AttributeError: _reverse_property

Question

Ich habe Probleme beim Arbeiten und lernen SQLALCHEMY und ich denke, das Problem ist mit meinem back_populate in Beziehungen zu tun, aber ich konnte es nicht aussprechen. Kannst du mir bitte in die richtige Richtung zeigen?

Die Tische sind erfolgreich erstellt und alles scheint in Ordnung zu sein, bis ich einen neuen MailProvider versuchen und schaffen, die diesen Fehler verursacht:

Traceback (most recent call last): 
    File "C:/Users/Music/.PyCharm2016.2/config/scratches/scratch_7.py", line 71, in <module> 
    gmail = MailProvider(service_provider="gmail.com") 
    File "<string>", line 2, in __init__ 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\instrumentation.py", line 347, in _new_state_if_none 
    state = self._state_constructor(instance, self) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\util\langhelpers.py", line 754, in __get__ 
    obj.__dict__[self.__name__] = result = self.fget(obj) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\instrumentation.py", line 177, in _state_constructor 
    self.dispatch.first_init(self, self.class_) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\event\attr.py", line 256, in __call__ 
    fn(*args, **kw) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\mapper.py", line 2872, in _event_on_first_init 
    configure_mappers() 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\mapper.py", line 2768, in configure_mappers 
    mapper._post_configure_properties() 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\mapper.py", line 1708, in _post_configure_properties 
    prop.init() 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\interfaces.py", line 183, in init 
    self.do_init() 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\relationships.py", line 1632, in do_init 
    self._generate_backref() 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\relationships.py", line 1866, in _generate_backref 
    self._add_reverse_property(self.back_populates) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\orm\relationships.py", line 1574, in _add_reverse_property 
    other._reverse_property.add(self) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\util\langhelpers.py", line 840, in __getattr__ 
    return self._fallback_getattr(key) 
    File "C:\Users\Music\mailtesterV2\lib\site-packages\sqlalchemy\util\langhelpers.py", line 818, in _fallback_getattr 
    raise AttributeError(key) 
AttributeError: _reverse_property 

Mein Code:

from sqlalchemy import Column, ForeignKey, Integer, String, Boolean, DateTime 
from sqlalchemy.ext.declarative import declarative_base 
from sqlalchemy.orm import relationship, sessionmaker 
from sqlalchemy import create_engine 

engine = create_engine('sqlite:///:memory:', echo=True) 
Session = sessionmaker(bind=engine) 

Base = declarative_base() 

class MailProvider(Base): 
    __tablename__ = 'mail_provider' 

    id = Column(Integer, primary_key=True) 
    service_provider = Column(String(250), nullable=False) 

    imap_server = Column(String(250)) 
    imap_server_port = Column(Integer) 
    imap_server_ssl = Column(String(250)) 
    imap_server_port_ssl = Column(Integer) 
    imap_server_use_tls = Column(Boolean) 

    smtp_server = Column(String(250)) 
    smtp_server_port = Column(Integer) 
    smtp_server_ssl = Column(String(250)) 
    smtp_server_port_ssl = Column(Integer) 
    smtp_server_use_tls = Column(Boolean) 

class MailAccount(Base): 
    __tablename__ = "mail_account" 

    id = Column(Integer, primary_key=True) 
    email_address = Column(String(250), nullable=False) 
    imap_username = Column(String(250), nullable=False) 
    imap_password = Column(String(250), nullable=False) 
    smtp_username = Column(String(250), nullable=False) 
    smtp_password = Column(String(250), nullable=False) 
    provider_id = Column(Integer, ForeignKey('mail_provider.id'), nullable=False) 
    provider = relationship("MailProvider", back_populates="service_provider") 
    account_owner = Column(String(250), nullable=False) 

class SentMail(Base): 
    __tablename__ = "sent_mail" 

    id = Column(Integer, primary_key=True) 
    mail_uuid = Column(String(36), nullable=False) 
    time_sent = Column(DateTime(timezone=True), nullable=False) 
    sent_from_id = Column(Integer, ForeignKey('mail_account.id'), nullable=False) 
    sent_from = relationship("MailAccount", back_populates="email_address") 
    sent_to = Column(String(250), nullable=False) 
    msg_subject = Column(String(250)) 
    msg_body = Column(String) 
    send_status = Column(String(500)) 

class ReceivedMail(Base): 
    __tablename__ = "received_mail" 

    id = Column(Integer, primary_key=True) 
    sent_mail_id = Column(Integer, ForeignKey('sent_mail.id'), nullable=False) 
    sent_mail = relationship("SentMail", back_populates="mail_uuid") 
    time_received = Column(DateTime(timezone=True), nullable=False) 


MailProvider.accounts = relationship("MailAccount", back_populates="provider", order_by="MailAccount.id") 
MailAccount.mails_sent = relationship("SentMail", back_populates="mail_uuid", order_by="SentMail.time_sent") 
SentMail.received_mails = relationship("RecievedMail", back_populates="received_time", order_by="RecievedMail.received_time") 

Base.metadata.create_all(engine) 
session = Session() 
gmail = MailProvider(service_provider="gmail.com") 

session.add(gmail) 
session.commit() 

Answer 1

Beziehung back_populates Referenz andere Beziehungen, keine Spalten.

Überarbeitete Code:

from sqlalchemy import Column, ForeignKey, Integer, String, Boolean, DateTime 
from sqlalchemy.ext.declarative import declarative_base 
from sqlalchemy.orm import relationship, sessionmaker 
from sqlalchemy import create_engine 

engine = create_engine('sqlite:///:memory:', echo=True) 
Session = sessionmaker(bind=engine) 

Base = declarative_base() 

class MailProvider(Base): 
    __tablename__ = 'mail_provider' 

    id = Column(Integer, primary_key=True) 
    service_provider = Column(String(250), nullable=False) 

    imap_server = Column(String(250)) 
    imap_server_port = Column(Integer) 
    imap_server_ssl = Column(String(250)) 
    imap_server_port_ssl = Column(Integer) 
    imap_server_use_tls = Column(Boolean) 

    smtp_server = Column(String(250)) 
    smtp_server_port = Column(Integer) 
    smtp_server_ssl = Column(String(250)) 
    smtp_server_port_ssl = Column(Integer) 
    smtp_server_use_tls = Column(Boolean) 

    accounts = relationship("MailAccount", back_populates="provider") 

class MailAccount(Base): 
    __tablename__ = "mail_account" 

    id = Column(Integer, primary_key=True) 
    email_address = Column(String(250), nullable=False) 
    imap_username = Column(String(250), nullable=False) 
    imap_password = Column(String(250), nullable=False) 
    smtp_username = Column(String(250), nullable=False) 
    smtp_password = Column(String(250), nullable=False) 
    provider_id = Column(Integer, ForeignKey('mail_provider.id'), nullable=False) 
    provider = relationship("MailProvider", back_populates="accounts") 
    account_owner = Column(String(250), nullable=False) 
    mails_sent = relationship("SentMail", back_populates="sent_from", order_by="SentMail.time_sent") 

class SentMail(Base): 
    __tablename__ = "sent_mail" 

    id = Column(Integer, primary_key=True) 
    mail_uuid = Column(String(36), nullable=False) 
    time_sent = Column(DateTime(timezone=True), nullable=False) 
    sent_from_id = Column(Integer, ForeignKey('mail_account.id'), nullable=False) 
    sent_from = relationship("MailAccount", back_populates="mails_sent") 
    sent_to = Column(String(250), nullable=False) 
    msg_subject = Column(String(250)) 
    msg_body = Column(String) 
    send_status = Column(String(500)) 
    received_mails = relationship("ReceivedMail", back_populates="sent_mail", order_by="ReceivedMail.time_received") 

class ReceivedMail(Base): 
    __tablename__ = "received_mail" 

    id = Column(Integer, primary_key=True) 
    sent_mail_id = Column(Integer, ForeignKey('sent_mail.id'), nullable=False) 
    sent_mail = relationship("SentMail", back_populates="received_mails") 
    time_received = Column(DateTime(timezone=True), nullable=False) 

Base.metadata.create_all(engine) 
session = Session() 
gmail = MailProvider(service_provider="gmail.com") 

session.add(gmail) 
session.commit()